This invention relates generally to water quality control and purification systems and in particular to a water purification system and apparatus that creates an integrated, small-scale marine or aquatic ecosystem particularly useful as a home, school, office, or laboratory aquarium.
For centuries, man has attempted to re-create a small portion of the underwater environment, but this has proven to be an especially difficult task, particularly for a salt water environment The difficulties of keeping marine life alive in captivity have been described as "witchcraft mixed with a little science."
Since fresh water organisms are more adapted to a changeable environment, generally past experience with fresh water culture has been more successful than with sea water, though not without considerable difficulties.
In the past, the problem has been said to be instability of water (particularly sea water) and its organic constituents, when confined in an aquarium or circulatory systems, and the characteristic inability of marine and to lesser extent aquatic organisms to adjust to changes in their environment. The necessary components of a proper environment were thought to include a chemically inert water system, a low ratio of animal life to volume of water, the control of bacteria, and the elimination of metabolic waste products.
In addition, since an aquarium contains a fixed volume of water, which is used repeatedly, its ecology is fragile and dependent upon many interrelated physical, chemical, and biological factors. These include the oxygen-carbon dioxide cycles, the nitrogen and phosphorus cycles, and the balance of particulate matter. With respect to the latter, soluble and insoluble organic and inorganic waste materials, which are excreted by aquatic specimens or which are formed by the natural decomposition by bacteria of plant and animal tissues, must be removed from the aquarium environment. This particulate matter, along with dissolved organic compounds, is converted by bacterial action to carbon dioxide and dissolved nutrients. The concentration of such metabolites in a fixed volume of water must be kept carefully balanced so that the system does not become overloaded, particularly by ammonia, carbon dioxide and nutrients, and at the same time depleted of oxygen.
In order to capture a complex aquatic environment in an aquarium, particularly a saltwater environment in a small home, school, office, or laboratory aquarium, it is necessary to simulate the natural environment. All of the physical and chemical components of the environment must be provided. Then the balance of plant and animal life and their proper relation to the volume of water must be adjusted. Previous attempts to do so on the scale of a home aquarium have not given sufficiently satisfactory results.
Traditional home aquaria have re-created only a limited part of the natural environment. Water quality is maintained by mechanical filters that remove sediment, by biological (bacteriological) filters that break down the first product of animal excretion, ammonia, and by systems for bubbling air through the water in order to add oxygen. Lighting is generally kept at a minimum in order to avoid algal blooms due to inherently high nutrient levels.
This traditional system has numerous inadequacies. Although biological filters remove particulate organic matter and ammonia, they can leave the system high in reactive nutrients. In addition, they consume oxygen and produce carbon dioxide. The latter compound has the undesirable effect of lowering the pH of the water, i.e., making the water more acidic. The filters used for organic sediment control can filter out plankton, whose presence is desirable in marine and aquatic ecosystems. Simple on/off lighting does not adequately simulate dawn and dusk, the time of greatest stress in the ecosystem. Finally, the low level of light does not add sufficient energy to support a complete and complex ecosystem. In sum, these systems are inherently unstable, and the organisms in them are prone to poor health and disease. Therefore, even the successful masters of the "witchcraft" of aquarium management have been limited to keeping only selected fish and a few invertebrates.
Several attempts have been made to improve upon conventional mechanical and bacteriological filtration of water by adding other filtration systems to the aquarium. See, for example, U.S. Pat. Nos. 3,929,101 to Katz, 3,848,567 to Garber, and 3,557,753 to Dantoni, which combine an algal filtration system with the standard bacteriological filter. Another approach has been to add biochemical filtration to the standard bacteriological filter in order to control pH. See U.S. Pat. No. 3,387,587 to Kelley. These approaches address one of the many components of an aquatic ecosystem, but they are a long way from duplicating such an ecosystem in a home aquarium.
A more system-oriented approach to water purification is disclosed in U.S. Pat. No. 3,155,609 to Pampel. This patent discloses a complex system of plumbing and chambers for directing water turbulence, calcium treatment, and a variety of limited band light treatments to purify eutrophic water from a biological source of pollution. The light treatments are regarded as having a variety of photochemical effects, and photosynthesis is used in one section of the system. Although the inventor asserted a microcosm-like control of a closed water system, there is no effort to use natural energy sources relative to real ecosystems. Also, there is no effort directed toward optimizing photosynthetic efficiency. Moreover, the purifying unit is separate from the biological unit being purified. Thus, the Pampel system is not an integrated system that could serve as a marine or aquatic ecosystem, particularly on a small scale.
Newer methods of water quality control utilize bacterial conversion of nitrogen to the gaseous form (denitrification). However, this is a process of low efficiency, and it does not handle phosphorus or lower carbon dioxide.
A major step forward in water purification and aquatic-marine ecosystem simulation was made with the invention of the algal turf scrubber. The scrubber is described in U.S. Pat. No. 4,333,263 to Adey, which is incorporated herein by reference. This process provided the relatively high efficiency of photosynthesis for water purification in controllable form in the marine or aquatic environment. That algal turf scrubber utilizes dense mats of benthic microalgae which are subjected to light and water surge motion created by a wave generator to promote metabolic cellular-ambient water exchange as a means of removing carbon dioxide, dissolved nutrients and organic compounds, and a variety of pollutants from natural or waste water. The algal turf scrubber also injects oxygen into the aqueous environment. An important aspect of that invention is the use and optimization of wave surge motion to enhance the exchange of metabolites between the algal cells and the water media. By optimizing the surge motion and by continuously harvesting the algae in a young, rapidly growing state, the photosynthetic efficiency of the algae is enhanced and optimized.
Such an algal turf scrubber has been used in a large, man-made marine ecosystem. See W. H. Adey, "The Microcosm: A New Tool For Research," in Coral Reefs (Springer-Verlag 1983), pgs. 193-201, which is incorporated herein by reference. It allowed the recreation of a marine ecosystem on a large scale (1800 gallons) for the first time. No bacteriological filtration, chemical conditioning, or air bubbling was needed. The use of the algal turf scrubber also permitted the use of appropriately intense lighting, equivalent to sunlight, thereby providing sufficient naturally-derived energy for the maintenance of a complex ecosystem containing numerous and diverse living organisms.
However, until the present invention, it was not possible to operate such a complete ecosystem on a small scale, such as in a home, school, office, or laboratory aquarium involving approximately 40-150 gallons of water. The necessary efficiency could not be achieved on such a compact scale.
Another inadequacy of the traditional system for home aquaria is the inability to simulate tidal displacement. In natural systems, tide will change the level of the water surface in a cyclical period. The cycle includes a daily cycle as well as a monthly cycle. For example, the tides at "spring" levels corresponding to sun and moon together having maximum effect have a higher amplitude of difference between the high tide and the low tide as compared to other times of the month. Thus, there is a need for a simple yet effective means to raise and lower the water surface in the aquaria on both a daily basis and a bi-weekly basis.